Third harmonic generation via dendrimers of four generations

We report on third harmonic generation of E-O active dendrimers dispersed in polycarbonate matrix. Four kinds of polyester type dendrimers G0, G1, G2 and G3 containing azobenzene in the core used as third order nonlinear optical active chromophores were prepared as guest-host type system based on polycarbonate matrix spin-coated on a glass substrate. Third harmonic generation was measured while exciting the samples with fundamental wavelength 1.064 ¿m. Non-linear third-order susceptibility ¿(3) for different generations of dendrimers was evaluated

Light-induced reflectivity transients in black-Si nanoneedles

© 2015 Elsevier B.V. All rights reserved. The change in reflectivity of black-Si (b-Si) upon optical excitation was measured by the pump-probe technique using picosecond laser pulses at 532 (pump) and 1064 nm (probe) wavelengths. The specular reflection from the random pattern of plasma-etched b-Si nano-needles was dominated by the photo-excited free-carrier contribution to the reflectivity. The kinetics of the reflectivity were found to be consistent with surface structural and chemical analysis, performed by scanning and transmission electron microscopy, and spectroscopic ellipsometry. The surface recombination velocity on the b-Si needles was estimated to be ~102cm/s. Metalization of b-Si led to much faster recombination and alteration of reflectivity. The reflectivity spectra of random b-Si surfaces with different needle lengths was modeled by a multi-step refractive index profile in the Drude formalism. The dip in the reflectivity spectra and the sign reversal in the differential reflectivity signal at certain b-Si needle sizes is explained by the model

The hard X-ray Photon Single-Shot Spectrometer of SwissFEL - Initial characterization

SwissFEL requires the monitoring of the photon spectral distribution at a repetition rate of 100 Hz for machine optimization and experiment online diagnostics. The Photon Single Shot Spectrometer has been designed for the photon energy range of 4 keV to 12 keV provided by the Aramis beamline. It is capable of measuring the spectrum in a non-destructive manner, with an energy resolution of Δ E/E = (2-5) × 10-5 over a bandwidth of 0.5% on a shot-to-shot basis. This article gives a detailed description about the technical challenges, structures, and considerations when building such a device, and to further enhance the performance of the spectrometer

Geometrical management of optical vortices by closed-path metallic nanoslits

We propose and experimentally demonstrate a geometrical approach to the controlled generation of optical phase singularities at small scale by using metallic nanostructures, thereby offering a novel strategy towards singular nanophotonics

Engineering and Localization of Quantum Emitters in Large Hexagonal Boron Nitride Layers.

Hexagonal boron nitride is a wide-band-gap van der Waals material that has recently emerged as a promising platform for quantum photonics experiments. In this work, we study the formation and localization of narrowband quantum emitters in large flakes (up to tens of micrometers wide) of hexagonal boron nitride. The emitters can be activated in as-grown hexagonal boron nitride by electron irradiation or high-temperature annealing, and the emitter formation probability can be increased by ion implantation or focused laser irradiation of the as-grown material. Interestingly, we show that the emitters are always localized at the edges of the flakes, unlike most luminescent point defects in three-dimensional materials. Our results constitute an important step on the roadmap of deploying hexagonal boron nitride in nanophotonics applications

Plasmonic sensor: Towards parts-per-billion level sensitivity

We have developed a plasmonic gas sensing system using transmissive (metal hole array) and scattering (rough surface of Au film) plasmonic materials in an integrating sphere geometry. The combination of transmissive and reflective plasmonic materials significantly enhances the detection threshold by way of surface-enhanced infrared absorption. Here, we first investigate the individual sensing enhancement contributions for each of the plasmonic materials and reveal the path towards applications in high-sensitivity gas detection